Sleep-disordered breathing is a common and serious cause of morbidity during childhood. Though the diagnosis of frank obstructive sleep apnea syndrome (OSAS) is readily achieved by overnight polysomnography, the recognition of more subtle forms of obstructed breathing, such as the upper airway resistance syndrome (UARS) are not. UARS is characterized by brief, repetitive arousals during sleep associated with increased respiratory effort, in the absence of overt apnea/hypopnea or gas exchange abnormalities. The diagnosis of UARS is important insofar as it has been associated with profound physiological and neurobehavioral consequences. The "gold standard" for diagnosing UARS is esophageal manometry, which is invasive and cumbersome. Our research proposal hypothesized that the physiological determinants of sleep-disordered breathing in children could be characterized using non-invasive measures of flow limitation, respiratory effort and autonomic arousal. Otherwise normal children between 2 - 6 years of age who presented to the outpatient clinic with symptoms of sleep-disordered breathing were asked to participate in the study. Subjects underwent a standard overnight polysomnographic montage with the addition of esophageal manometry recording, pulse transit time measurement, respiratory inductance plethysmography and heart rate variability analysis. The definitive diagnose of sleep-disordered breathing, including UARS was made using esophageal manometry, which was then compared with the noninvasive indices. The ability to diagnose UARS using noninvasive tools will extend treatment options to many children with physiological and neurocognitive sequelae of sleep-disordered breathing.